Python Notes

Tuesday, December 14, 2004

Forget the GUI (long live the GUI!)

There was a time, not a really long ago, when business programming meant basically processing data. The visual interface options were really limited, so much more time was spent in the business logic than in the UI part of the system. Now times have changed for better, and GUIs are the norm; in fact, it's so common place now as to make one wonder how were things done before. For many programmers, prototyping means baking a visually decent, but barely functional sketch of the software that they hope to deliver. It's amazing how many of those so called "prototypes" end up being used as the final application, with a lot of shortcomings.

That's all to present a proposal, that may sound radical, but it really isn't. Forget the GUI. I mean: forget it while writing the prototype of the software.

This idea may seem silly, or even counter-intuitive, due to several factors:
  • Many people today relate the idea of programming to the one of making something visible. Managers, specially.
  • Rapid development languages are focused toward visual development. This makes for a great temptation, specially for novices.
  • Due to the combination of the aforementioned reasons, it's pretty easy to fake development using visual development tools. In the process the programmer usually falls prey of its own device, having to maintain the code that was supposed to be a prototype as the real product, thus never having the time to finish the product.

So what's the revolutionary "forget the GUI" idea? It's basically about a change in the approach for the initial phases of development. Instead of focusing efforts on the GUI part (which is really a mistake, as any serious system analyst will note), focus the effort on the prototyping of the business objects. All the development is done in this phase using a combination of techniques, one of them at least 40 years old -- Test Driven Development, and batch processing.

Test Driven Development (see also TDD on C2 Wiki for a discussion on the topic) is one relatively new buzzword. It's one of the techniques associated with Extreme Programming, and it's got a fair share of discussion, praises and critics over the past few years. On the other hand, batch processing is one of the old-style programming techniques that have a decidedly bad fame attached to it. But if applied correctly, it's still highly useful. In fact, all those scripts that process huge log files are nothing more than batch processes in a disguise (just don't tell managers about it).

The combination works like this: on the initial phases of the system development, focus on the prototyping of the business objects. Model real processes as they happen; write objects, fill them with data by hand (by assigning values directly to their properties), and implement simple routines that simulate the process. Dynamic languages like Python are wonderfully well suited to this approach to coding. Using a TDD approach, write the test cases based on this input. Determine what should happen for each case, and make a test case: fill objects with data, call a processing method, check the resulting data.

All the data that you have at this point will be coded in the test scripts, that act in a sense as a simple batch processing system. Everytime you run the test system, you are in fact running a batch that is the prototype for the entire application. Of course, tests sometimes need to force the system limits, or even feed bad data to the system. But you can separate stress tests from the actual system simulation objects, so you have a valid database after you finish processing the data.

This approach has many advantages. On one hand, it does not give the project the immediate visibility that a GUI prototype gives. But it compensates for this with a greatly simplified development environment, where the programmer can focus on the business rules. One of the most time consuming parts of visual development is keeping the visual part of the program (data entry forms, for example) in sync with the business rules. If you change the schema, you have to change the forms; in some cases, the change propagates to several modules. To make things worse, a simple "find & replace" is not very helpful at this point. By writing a "batch style" prototype, the programmer can bypass this step, and write the GUI only after the schema is already stable, and subject to smaller changes.

Another advantage of this approach is the modularization. In general, conventional GUI programs suffer from the tendency of being monolithical, partially due to the very development model that the RAD tool emphasizes. Writing the batch processing scripts helps to isolate the underlying system API from the visual presentation of data. The system becomes easier to test, and also, easier to automate with user-level scripts.

So the conclusion is: Forget the GUI, long live the GUI. Because in the end, the application will have a GUI. But it will be mounted over a clean, well modularized foundation, that is testable and easily scriptable. That's more than offset any disadvantage that the lack of a preliminary visual prototype could possibly cause.

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